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JAPANESE KNOTWEED

• Hollow, bamboo-like stems with purple speckles• Can reach up to 3m high• Flowers from August to October• Thick and knotty underground rhizomes (stems) • When cut open, the rhizomes have a bright orange centre• Rhizomes can extend for up to 2m deep and 7m across from a parent plant

Japanese Knotweed is an invasive, non-native plant which can cause extensive damage to foundations, roads and other constructions. It can also choke and damage riverbanks, as it out-competes native wildlife. It can regenerate very easily via small root and stem fragments, so extreme care must be taken to avoid spreading it to other areas.

If you spread Japanese Knotweed outside of a project site boundary, you and the company may be liable to prosecution.

HOW TO PREVENT JAPANESE KNOTWEED FROM SPREADINGJapanese Knotweed generally spreads from one site to another by soil excavation and disturbance—parts of the plant may be moved around the site, imported on to the site in soil and rubble (including fly-tipping of garden waste) or exported off-site in waste containers and on vehicles.

On no account should excavation, vegetation clearance or vehicle/pedestrian movement take place within the 15m exclusion zone.

Young purple shoots of Knotweed seedlings

Medium shoots of Knotweed in vegetation stage

Flowers of a mature Knotweed plant

If you have identified Japanese Knotweed on your project site, inform the client/engineer immediately. Because the root system is extensive, no work should be undertaken within 15m of the nearest stand of Knotweed. If possible, erect fencing or barriers to prevent anyone going near the plant.

HIMALAYAN BALSAM

Flowers of a mature Himalayan Balsam plant

Himalayan Balsam seed pods • Lance-like leaves with serrated edges• Pinkish red, brittle and hollow stems• Can reach up to 3m high• Flowers from June to October• Purple/pink flowers (rarely white), shaped like a policeman’s helmet• Look out for distinctive pods, which can spread seeds up to 7m

Himalayan Balsam grows quickly in dense stands, suppressing native vegetation. When the plants die back in the autumn, areas like river and railway embankments can be left bare and prone to erosion. They can spread rapidly (up to 645km2 per year), as the seed pods are easily disturbed. When the pods burst, they release seeds into the soil and watercourses, and they can be transported over great distances. Once released, the entire seed population germinates at the same time to form a dense stand in spring.

HOW TO PREVENT HIMALAYAN BALSAM FROM SPREADINGHimalayan Balsam’s seed pods are a major problem. The plant spreads very quickly when the pods burst and release their seeds.

Where possible, areas containing the plant should be fenced off to at least 3m away. Fenced areas should have appropriate warning signs, and all staff on site must be told about the plant’s location to prevent accidental disturbance.

On no account should excavation, vegetation clearance or vehicle/pedestrian movement take place within the 3m exclusion zone. All measures should be taken to prevent the plant or its seeds being transported off site on machinery and vehicles, or in the soil.

Mature Giant Hogweed

GIANT HOGWEED

As well as having similar environmental effects, Giant Hogweed is a health hazard. Stems and leaves have small, fine hairs coated in a poisonous, highly caustic sap. This causes painful blistering and severe irritation when it comes into contact with skin. A reaction can occur up to 48 hours after contact, with the skin becoming hyper sensitive to ultraviolet light resulting in burns and swelling.

Initially the skin turns red and starts itching, before turning to blisters. The blistering heals slowly, and can develop into phyto-photodermatitis—a type of dermatitis which flares up in sunlight and for which there is no straightforward treatment. Light sensitivity and skin discolouration is often permanent, and blindness can result from contact with the eyes.

HOW TO PREVENT GIANT HOGWEED FROM SPREADINGIf Giant Hogweed is identified on site, the Site Engineer has a duty to protect the public and site personnel. Adequate protective clothing (not light fabrics) should be supplied to anyone at risk of coming into contact with the plant. The surrounding area should be fenced off if possible, with an exclusion zone of at least 3m. Health and Safety information must be made available to detail the risks and the action to be taken in case of contact.

It is an offence to enable Giant Hogweed to grow in the wild. This includes spreading the species or transferring polluted ground material from one area to another. Any Giant Hogweed polluted soil or plant material to be discarded is classed as controlled waste under Part II of the Environmental Protection Act 1990 and should be accompanied by the appropriate Waste Transfer documentation. Breach of the duty of care for controlled waste is an offence that could result in penalty fines and imprisonment.

If skin contact does occur, immediately cover the affected area and wash with soap and water while avoiding direct sunlight. Medical advice should then be sought as quickly as possible.

• Thick stem, with dark red or purple spots with fine hairs

• Can grow up to 5m high

• Can take up to 4 years before flowering in June/July

• Very large leaves—up to 1.5m across near the bottom of the plant

• Dark green leaves, spiked at the end

• Produces a single large, white, umbrella-like flower head containing several hundred smaller flowers

• Can produce up to 50,000 seeds a year

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For more advice about invasive species and environmental issues, please contact Chris Swainstoncswainston@geotechnics.co.uk

For further information on Health and Safety, please contact Michael Coatesmcoates@geotechnics.co.uk